Support

Stream privacy settings

Streams are similar to chatrooms, IRC channels, or email lists in that they
determine who receives a message. There are three types of streams in Zulip.

Public: Anyone other than guests can join, and anyone (other
than guests) can view the complete message history without joining.

Private, shared history: You must be added by a member of the stream. The
complete message history is available as soon as you are added.

Private, protected history: You must be added by a member of the
stream. You only have access to the messages that are sent after you are added.

Privacy model for private streams

At a high level:

Organization admins can see and modify most aspects of a private stream,
including the membership and estimated traffic. Admins generally cannot see stream
messages or do things that would indirectly give them access to stream
messages, like adding members or changing the stream privacy settings.

Non-admin members cannot easily see which private streams exist, or interact with
them in any way until they are added. Given a stream name, they can figure
out whether a stream with that name exists, but cannot see any other
details about the stream.

From the perspective of a guest, all streams are private streams, and they
additionally can't add other members to the streams they are subscribed to.

There are two situations in which an organization administrator can access
private stream messages:

Administrators can change the ownership of a bot. If a bot is subscribed
to a private stream, then an administrator can get access to that stream by
taking control of the bot, though the access will be limited to what the
bot can do. (E.g. incoming webhook bots cannot read messages.)

Detailed permissions

Public streams

Org admins

Members

Guests

Join

✔

✔

Unsubscribe

◾

◾

◾

Add others

✔

✔

See subscriber list

✔

✔

◾

See full history

✔

✔

◾

See estimated traffic

✔

✔

◾

Post

✔

✶

✶

Change the privacy

✔

Rename

✔

Edit the description

✔

Remove others

✔

Delete

✔

✔ Always

◾ If subscribed to the stream

✶ Configurable. Org admins and
Members can, by default, post to any public stream, and Guests can
only post to public streams if they are subscribed.